Fluid die cushion unit with air saver

ABSTRACT

A self-contained die cushion for use on a power press wherein the normal cushion chamber includes a separate reservoir sealed from the rest of the chamber and having a movable wall in the form of a diaphragm and a fixed perforated wall to allow the fluid in the reservoir to assist in biasing the die cushion upwardly, but preventing exhaust of the reservoir when the chamber is exhausted to drop the cushion for changing or repairing dies in the press.

United States Paten Inventor Appl. No. Filed Patented Assignee Company Grand Rapids, Mich.

FLUID DIE CUSHION UNIT WI'II-I AIR SAVER 2 Claims, 9 Drawing Figs.

11.8. C1 267/119, 2% Int. Cl. 182111 24/02, F16f9/04, Fl 1f 13/00 Field 011 Search 100/269 A; 267/119, 120,126

II I I i Primary Examiner-Arthur L. La Point Assistant Examiner--Howard Beltran Attorrzey--Meyer, Tilberry and Body ABSTRACT: A self-contained die cushion for use on a power press wherein the normal cushion chamber includes a separate reservoir sealed from the rest of the chamber and having a movable wall in the form of a diaphragm and a fixed perforated wall to allow the fluid in the reservoir to assist in biasing the die cushion upwardly, but preventing exhaust of the reservoir when the chamber is exhausted to drop the cushion for changing or repairing dies in the press.

Patented Aug. 3, 1971 3 Sheets-Sheet 1 v c b Fl 9 I I 2m n v 2|Q I 1 2|2 I ""1"" W INVENTOR D R HLD H K R HFT TTOIZNEYS runs lDlllE CUSHION Tlhlil'll WTTllil Alfih SAT/Eh This application is a division of application Ser. No. 653,116, filed July 13, 1967, now US. lPatNo. 3,511,491.

The present invention relates to the art of self-contained die cushions, and more particularly to a self-contained die cushion having an air saver or reservoir incorporated therewith.

This invention is particularly applicable for use in a power press wherein depending rods are used to support a holddown ring of a drawing die, and it will be described with particular reference thereto; however, it is appreciated that the invention has much broader applications and may be used in various other environments wherein a die cushion is required.

Many dies used within power presses incorporate holddown rings or other auxiliary elements which are controlled, to a certain extent, by a die cushion located below the bolster of the power press. These die cushions talre a variety of forms; however, the most common die cushion includes two telescoped sleeves with end walls defining an internal cushion chamber filled with a compressible fluid which biases the upper sleeve in an upwardly direction. A plurality of rods extending downwardly from the die within the press rests upon the upper sleeve, generally known as a pressure pad. These rods coact with movable elements within the die so that the pressure pad is forced downwardly by the rods during the downward strolre of the press. The downward movement of the upper sleeve or pressure pad compresses the fluid within the cushion chamber so that the rods are forced in an upward direction by the pressure pad during the upward stroke of the power press. The volume of air, or other other compressible fluid, within the chamber of the die cushion is quite large to provide the necessary biasing action for the downwardly extending rods. This presents a substantial diificulty.

When a die is to be repaired or replaced, the die cushion must be dropped into an inoperative position. One common way of accomplishing this is to exhaust most of the fluid from the chamber of the die cushion. This requires a substantial amount of time to exhaust and then replace the large volume of fluid within the die cushion. in an effort to reduce the time for exhausting and filling the chamber of the die cushion, relatively large supply hoses have been used. These are expensive, and they do not substantially reduce the total time required to drop the die cushion into its inoperative position and then raise the die cushion into its operative position. To overcome the disadvantages of this particular arrangement, it has been suggested that a fluid reservoir should be mounted adjacent the die cushion with a valve between the reservoir and the cushion. When the die cushion is to be dropped, the valve is opened to store fluid within the reservoir. The valve was then closed so that the fluid would remain in the reservoir. To raise the die cushion, the valve was again opened which allowed flow of fluid back to the die cushion. This again involved complex and expensive mechanical arrangements to accomplish the operation of the die cushion.

The structure explained above has been modified to provide the reservoir and valve within the die cushion itself. When this is done, the piping between the reservoir and the die cushion chamber is eliminated; however, certain inherent disadvantages are built in. The valve between the reservoir and die cushion must be operated, mechanically, from a position outside of the die cushion. Thus, a rod or other valve operating means must be provided internally of the die cushion. Also, when the valve becomes defective, the die cushion must be taken apart and repaired. By providing internal valving within the die cushion, it is difficult to provide hydraulic snubbers or hydraulic holddowns which are generally used in the operation of a die cushion. A hydraulic snubber is used to control the upward movement of the die cushion so that it is somewhat out of phase with the upward stroke of the power press. The hydraulic holddown is utilized to lock the die cushion in a downward position when the die cushion is not be be used.

The disadvantages of the prior die cushions are completely overcome by the present invention which is a completely new concept to the art of die cushions and includes a simplified structure which will allow movement of the die cushion between its upward operative position and its lower inoperative position.

in accordance with the present invention, there is provided an improvement in a self-contained die cushion, comprising a movable, operative member and fluid means for biasing the member in a given direction for movement between points a and b wherein the fluid means includes means defining a cushion chamber filled with a compressible fluid and having a total volume V, or V when the member is at point a and a total volume V or V when the member is at point 12, V being greater than V Also provided is a means defining a sealed fluid filled reservoir within the chamber with at least one movable exterior wall, this reservoir having variable volume V which forms part of the volume of the chamber and is, at all times, substantially less than volume V-,,. Also provided are means for exhausting fluid from the chamber while the reservoir remains filled with fluid. in this manner, the die cushion may be dropped by exhausting only a portion of the cushion chamber. During normal operation of the die cushion, the filled reservoir within the chamber coacts through the movable external wall to provide a continuous, relatively large volume of air against which the die cushion operates. The improvement to the device defined above is the formation of the sealed fluid chamber as a flexible diaphragm which defines volume V and a fixed rigid wall means for limiting the movement of the diaphragm in the volume expanding direction.

The primary object of the present invention is the provision of a self-contained die cushion which is inexpensive to produce, usable in existing presses without modification and easily and rapidly dropped into the inoperative position and raised into the operative position with a minimum of fluid.

Another object of the present invention is the provision of a self-contained die cushion which requires a lesser amount of air, or fluid, to shift from the inoperative position to the opera tive position.

Yet another object of the present invention is the provision of a self-contained die cushion which incorporates two separate, isolated fluid compartments in the cushion chamber, both of which coact to provide the biasing action of the cushion and one of which is exhausted to drop the cushion into its inoperative position, which chamber is defined by a flexible diaphragm.

These and other objects and advantages will become apparent from the following description used to illustrate preferred embodiments of the invention as read in connection with the accompanying drawings in which:

lFlG. l is a partial, cross-sectional view illustrating, somewhat schematically, the structure to which this invention is an improvement.

FIG. 2 is a partial, crosssectional view illustrating a modification of the structure as shown in Phil. 1 with one aspect of the present invention shown;

FIGS. 3-5 are partial, cross-sectional views illustrating certain modifications of the structure shown in FIGS. 1 and 2;

MG. 6 is a cross-sectional view illustrating the preferred embodiment of the main aspect of the present invention;

FIG. '7 is a partial, cross-sectional view illustrating the operational characteristics of the embodiment of the invention illustrated in H6. 6;

HG. it is an enlarged, cross-sectional view illustrating still a further modification of the present invention; and,

FIG. 9 is a partial cross-sectional view showing the operating characteristics of the embodiment of the invention illustrated in FIG. E.

Referring now to the drawings, wherein the showings are for the purpose of illustrating preferred embodiments of the in vention only and not for the purpose of limiting the same, HO. 1 shows a self-contained die cushion A which is mounted on a support plate B attached to the under frame of a press (not shown) by a plurality of rods lit), 12.. The general operation of the die cushion is well known in the power press art; therefore, further discussion of the press itself, except with regard to the general operation of the die cushion, is not required.

Self-contained die cushion A includes a fixed sleeve 20 having a lower flange 22 secured onto a lower end wall 24 by a plurality of circumferentially spaced bolts 26. In like manner, bolts 28 secure the wall 24 onto the support plate B. An appropriate seal, such as O-ring seal 30, is provided between flange 22 and wall 24. Sleeve 20 also includes an outer bearing surface 32 which terminates at a recess 34 to form an abutment 36. Adjacent the upper portion of sleeve 20 there is provided appropriate seal 38, for a purpose which will be apparent from the further description of this embodiment. Also at the upper end of sleeve 20 is a relatively large opening 40 defined by a flange 42 having a lower abutment 44.

Reciprocally and telescopically received on sleeve 20 is a movable sleeve, or pressure pad, 50 which forms the operative member of the die cushion, in a manner to be described later. Sleeve 50 has an upper end wall 52, an inner mounting surface 54 slidably received on surface 32, and a lower stop 56 adapted to coact with abutment 36 to prevent withdrawal of sleeve 50 from sleeve 20. End wall 52 is provided with an upwardly facing, top surface 58 which is adapted to contact the lower end of operating rods 60. These rods are connected to various elements within the die mounted upon the bolster of a power press, in a manner well known in power press art.

Sleeves 20, 50 combine to form the total air chamber, hereinafter referred to as the internal cushion chamber 70 which is filled with pressurized fluid from an input line 72. Line 72 includes a branch 74 communicated with the lower portion of chamber 70 and a branch 76 communicated with the upper portion of chamber 70. This last-mentioned communication is through a passage 80, line 82, check valve 84, and control valve 86. The valve 86 is positioned as indicated in FIG. 1. The upper portion of chamber 70 is communicated with pressurized fluid from input line 72. Check valve 84 prevents fluid flow from the upper portion of chamber 70 to the supply line. In a like manner, a check valve can be provided in branch 74. To exhaust the upper portion of chamber 70, valve 86 could be manually actuated to connect line 82 with exhaust line 88. As so far described, the self-contained die cushion does not differ substantially from normal die cushions, except for flange 44 and certain aspects of the fluid inlet system.

In operation, rods 60 are connected onto certain elements within the die, such as knockout pins or a drawing ring. As the power press moves downwardly to close the die, rods 60 push sleeve 50 downwardly from an upper point a to a lower point b. This is done against the fluid bias of cushion chamber 70. As the power press moves upwardly, the fluid pressure within chamber 70 forces sleeve 50 back to its initial upper point a. The rods 60 are raised and perform the necessary function within the die, in accordance with the particular element being controlled by the rods. This procedure is repeated in each cycle of the power press. The total volume of fluid within chamber 70 is V or V,, when the sleeve 50 is at point a. In like manner, the total volume of chamber 70 is V or V,, when the sleeve 50 is at point b. Consequently, the difference in volume during the normal operation of die cushion A is V minus V Sleeve 20 is provided with a vertically movable wall 90, in the form of a piston having a top 92, a skirt 94, and a peripheral seal 96. Spring 98 biases the piston 90 in an upward direction. The movable wall 90 divides the total fluid volume of chamber 70 into an upper portion 100 and a lower portion 102. The lower portion has a variable volume V, which is dependent upon the position of the wall 90 with respect to sleeve 20. The volume V, is always substantially less than total volume V and volume V is also substantially less than total volume V Piston or wall 90 forms two isolated, separate portions in chamber 70. This has an extremely beneficial result which will be described later.

In operation, during normal function of the die cushion A, sleeve 50 moves between points a and b. This causes the fluid within chamber portions 100, 102 to be alternately com pressed and expanded. During this operation, piston or wall 90 oscillates within sleeve 20, and it does not substantially affect the operation of the die cushion. There is no interfluid flow between portions 100, 102 of the embodiment shown in FIG. 1. The interrelationship between these portions can be described as being mutual fluid pressure relationship or interforce transmitting relationship. In other words, the air or other fluid within portions 100, 102 functions in a manner generally simulating a situation where no wall or piston 90 is used.

When a die within the power press is to be repaired or replaced, the die cushion must be dropped. This is accomplished by exhausting portion 100 through valve 86. As the pressure within portion 100 is reduced, the pressure within portion 102 drives wall or piston 90 upwardly against abutment 44. In this manner, all of the fluid within portion 102 is retained within the die cushion, and it need not be replaced when the die cushion is again activated. To activate the die cushion, valve 86 is moved to the position illustrated in FIG. 1, and fluid pressure from input line 72 is forced through passage into portion 100. This immediately pumps up" the die cushion into its operative position.

It can be appreciated that only the volume of air necessary to fill chamber portion 100 is required to activate the die cushion, although the die cushion operates against the complete volume of fluid within both portions 100, 102. Since only a small volume of air is needed to activate the die cushion, the time required to activate and deactivate the die cushion is substantially reduced. Wall provides a positive seal between the fluid in portion and portion 102 when the die cushion is in its inactive position. There is no possibility of an inrush of air to portion 100 which would cause the die cushion to inadvertently move to its outward position while the die is being changed or repaired. The structure shown in FIG. 1 does not require complicated valving within the die cushion itself or other complicated mechanisms to provide an internal reservoir of fluid which is not periodically exhausted and replaced when the die cushion is to be dropped and again actuated. The relatively small volume of air needed to activate the die cushion coacts with the air remaining within portion 102 to provide normal operation of the die cushion.

Referring now to FIG. 2, a certain aspect of the present invention is shown wherein sleeve 20 is secured onto a mounting plate having a relatively large opening 112. A somewhat standard hydraulic locking device is secured to the lower end of plate 110. The control rod 122 for the hydraulic locking device extends from end wall 52 of sleeve 50, through an opening 124 in piston 90 having a bearing seal 126, and through opening of the device 120. The usual operating piston 134 is provided within the hydraulic locking device 120 and hydraulic fluid 136 is provided within the lower portion of sleeve 20 and is communicated by line 138 to the interior of the locking device 130. By utilizing the piston 90, the self-com tained die cushion may be provided with this standard hydraulic locking device without substantial modification of the die cushion. This is a substantial advantage because certain installations require the hydraulic locking device to hold the die cushion in an inoperative position during portions of a cycle or during various operations of the press itself.

Referring now to FIG. 3, a modification of the piston 90 is illustrated. Piston 90a is provided with an outer peripheral seal 140 and spaced vane seals 142, 144 for passage of rod 122. A spring 146 surrounds the rod 122 and biases the piston 90a in an upward direction.

Referring now to FIG. 4, a hydraulic snubber 150 is provided below the end wall 24 of sleeve 20. The control rod 122 having a lower piston 134 is connected to the end wall 52, as shown in FIG. 2. The hydraulic snubber 150 includes a control valving assembly 152 so that the movement of sleeve 50 in an upward direction after being first moved downwardly is controlled. This prevents abrupt upward movement of rods 60 during the operation of the die cushion shown in FIGS. 1 and 2. This embodiment of the invention illustrates the ease by which a standard hydraulic snubber may be incorporated within a die cushion constructed in accordance with the present invention.

Referring now to FIG. 5, a fixed sleeve 160 includes an inwardly extending flange 162 having a peripheral, lower seal 164. Reciprocal piston 170 includes a downwardly extending rod 172 which is received within a bore 174 having a spring 176 held in place by a plate 178. The piston 170 is provided with a plurality of peripheral grooves 180 which allow communication between the upper fluid portion 182 and the lower fluid portion 184 within sleeve 160. The peripheral grooves 180 are sealed when piston 170 is in its uppermost position against seal 164. Consequently, when a die cushion including this structure is to be dropped, fluid portion 182 and the interior of the upper sleeve 50, not shown is exhausted. This causes a rapid increase in the pressure differential across piston 170. This differential forces the piston in an upward direction to seal against seal 164. The pressure within fluid portion 184 maintains the piston in its sealed condition until fluid pressure is again introduced into the portion 182. This embodiment of the invention functions somewhat differently from the previously mentioned embodiments in that actual fluid communication is provided between the upper and lower fluid portions defined by the movable piston 170.

Attention is now directed to FIGS. 6 and 7. These figures illustrate the primary aspect of the present invention wherein a fixed sleeve 190 has an upper opening 192 which is covered by a flexible diaphragm 194. Above the diaphragm there is secured, onto the sleeve 190, a rigid perforated plate 196. The diaphragm divides the fixed sleeve into two separate, sealed, isolated fluid portions 200, 202. In FIG. 6, portion 202 is substantially zero. The diaphragm I94 flexes downwardly as sleeve 50 is forced downwardly by rods 60 and flexes upwardly as the rods 60 are allowed to move upwardly.

When portion 202 in the interior of sleeve 50 is exhausted, fluid within portion 200 is retained as diaphragm 194 moves upwardly into contact with plate 196, as shown in FIG. 6. A similar device is illustrated in FIGS. 8 and 9. ln this embodiment, a fixed sleeve 210 is provided with a support spider 212 onto which is mounted a rod guide 214. Rod 122, for a hydraulic snubber, or locking device, is received within the guide by hearing seals 216, 218. Since the central guide is used, an annular opening 220 is provided at the upper portion of the fixed sleeve, and this opening is sealed by an annular diaphragm 222. Above the diaphragm there is secured an annular perforated plate 224 which limits the upward extent or deflection of diaphragm 222. The diaphragm divides the interior of the fixed sleeve into separate, isolated, sealed portion 230, 232 with portion 232 being substantially zero when the diaphragm is in its upwardmost position, as shown in FIG. 8.

The present invention has been described in connection with certain structural embodiments; however, many modifi cations of these embodiments can be made without departing from the intended spirit and scope of the present invention as defined in the appended claims.

lclaim:

l. in a self-contained die cushion comprising a first sleeve, a second sleeve telescopically and reciprocally received on said first sleeve, said sleeves having end walls and combining to define a cushion chamber for a compressible fluid between said end walls, said second sleeve being biased upwardly by the fluid in said cushion chamber during operation of said die cushion and being dropped to an inoperative position when said die cushion is to be inoperative, means for dividing said chamber into separate, isolated first and second fluid chamber portions, means for limiting the expanded volume of said first portion to an extent incapable of preventing said second sleeve from dropping to an inoperative position upon exhausting of said second portion, and means for exhausting said second portion to drop said second sleeve to the inoperative position, the improvement comprisin said dividing means comprises a flexi le diaphragm secure within said first sleeve and said limiting means comprises a wall having openings therein above said diaphragm and secured to the upper portion of said first sleeve.

2. The improvement as defined in claim 1 wherein said first sleeve is mounted on a support plate and including a rod extending from the end wall of said second sleeve, through said chamber, through said dividing means, and through said plate, and means on said plate opposite said sleeves for holding said second sleeve in the inoperative position by said rod. 

1. In a self-contained die cushion comprising a first sleeve, a second sleeve telescopically and reciprocally received on said first sleeve, said sleeves having end walls and combining to define a cushion chamber for a compressible fluid between said end walls, said second sleeve being biased upwardly by the fluid in said cushion chamber during operation of said die cushion and being dropped to an inoperative position when said die cushion is to be inoperative, means for dividing said chamber into separate, isolated first and second fluid chamber portions, means for limiting the expanded volume of said first portion to an extent incapable of preventing said second sleeve from dropping to an inoperative position upon exhausting of said second portion, and means for exhausting said second portion to drop said second sleeve to the inoperative position, the improvement comprising: said dividing means comprises a flexible diaphragm secured within said first sleeve and said limiting means comprises a wall having openings therein above said diaphragm and secured to the upper portion of said first sleeve.
 2. The improvement as defined in claim 1 wherein said first sleeve is mounted on a support plate and including a rod extending from the end wall of said second sleeve, through said chamber, through said dividing means, and through said plate, and means on said plate opposite said sleeves for holding said second sleeve in the inoperative position by said rod. 